Gold complexes trans-effect

The gold complex, generated in situ from bis(4-isocyanocyclohexyl)gold(I) tetrafluoroborate and (A)-A-methyl-,V-[2-(dialkylamino)ethyl]-l-[(5)-r,2-bis(diphenylphosphino)ferrocenyl]eth-ylamine, is an effective catalyst for the aldol reaction of various aldehydes with methyl iso-cyanoacetate to give the trans- and cw-4,5-dihydro-l,3-oxazoles. Depending on the aldehyde, the transjeis product ratio ranges from 84 16 to 100 0, and the ee of the main diastereomer is between 72 and 97%26. 

Gold(III) complexes are quite labile. Tobe reports a stopped flow study of the kinetics of substitution reactions of MeOH in [Au(C6H5)(MeOH)Cl2] at temperatures up to 0 °C in methanol. For anionic reagents, Nu , complexation is via a solvento pathway. The trans effect order of Nu and Nu parallels that for reactions of [AuC ]", although the nucleophilic discrimination is lower than in other gold(III) complexes. The kinetics of replacement of a range of thiazoles, oxazoles, and substituted pyridines, L, from the square-planar complexes [AUCI3L] by Cl in... 

L = py or H2O) undergo solvolysis and oxidation to yield the mixed-valence compound [(bpy)2(0)Ru(V)0Ru(III)(py)(bpy)2r , which is an effective electrocatalyst for the oxidation of d to CI2 at pH < 4 and Cl" to OCr at pH > 11.8. Chloride ions have also been implicated as mediators in the oxidation of tetracyano-platinate(II) by gold(III) complexes and in the reversible redox reaction between trans,cis-[PtCl2(L)2(am)2] and [Pt(diars)2]. In both cases an atom-transfer redox mechanism is suggested. 

Gold NPs with azobenzene terminated alkane thiol chains chemisorbed on the surface and complexed with a-CD gave a photoresponsive suspension in water, in which the azobenzene photosomerization was as efficient as that of the free molecule. Preferential complexation of the allgrl chain in both trans- and ds-azobenzene configurations favoured the water solubility of the alkyl-aromatic moiety and the chemisorption process and reduced the interaction between the azobenzene units on the particle surface with positive effects on the efficiency of the photoisomerization. 

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